CHARLESTON, S.C. — A $10 million study will investigate whether a substance found in fish oil can reduce the risk of suicide among military veterans, where the rate is higher than in the population as a whole.

The three-year study of omega-3 fatty acids was announced Monday by the Medical University of South Carolina, the Department of Veterans Affairs and the National Institutes of Health.

In the controlled study being conducted for the Army, veterans already receiving mental health services will be given smoothies high in omega-3s for a six-month period. Others will be given a placebo.

Omega-3s are the main fats in the brain and are essential for neural function and normal brain development, said Bernadette Marriott, a professor in the Institute of Psychiatry at the Medical University of South Carolina and the principal investigator in the study.

“Through other studies it’s been found that they can help improve depression significantly,” she said.

Veterans Affairs estimates that 20 percent of the suicides in the nation are committed by veterans and that the rate among vets is almost twice as high as in the general population.

“One of the questions this study hopes to address is do we see a clinical effect that is strong enough that the military would then consider providing supplements to all military personnel, not just those who are already experiencing depression?” she said.

“This study will inform whether or not that is something we should think about doing or studying,” agreed Ron Acierno, a co-investigator at the university and the nearby Ralph H. Johnson VA Medical Center.

He said the study will help researchers decide if this is an avenue they should be investigating.

“If the intervention shows effects with people who are at risk, we then back it out a step and say here we have a minimal side-effect, inexpensive intervention that helps people with risk factors.” he said. “Does it work for everybody?”

Acierno said suicide rates among veterans are high both for those who have been deployed to war zones and those who have not.

He said it’s not really clear why, although the military and the Department of Veterans Affairs devote a lot of resources to help those who might have been scarred by combat.

But there is also stress for those who don’t get into combat.

“The military as an occupation is not a low-stress job,” Acierno said. “They interact with dangerous equipment and in dangerous conditions under training conditions of extreme stress.

“If you combine that with the stresses of daily life it may exacerbate what may have already been a depression or a suicidality.”